Automated crystal pulling system

ABSTRACT

An automated crystal pulling system utilizes a digital computer to control a Czochralski crystal puller. Crystal pull rate, crystal spin rate, crucible lift rate and crucible spin rate are monitored with tachometers, and the monitored signals are applied to controllers to control the respective motors and provide independent closed control loops, with each controller having a set point signal input from the computer. A sensor detects the output level of the radio frequency generator (induction heater) and applies a signal to a generator controller having a set point input from the computer, providing closed loop temperature control. A temperature control algorithm receives an input from a melt temperature sensor and calculates the set point to the generator controller. A diameter control algorithm receives an input from a crystal diameter sensor and calculates the set point to the crystal pull motor controller. A melt level control algorithm claculates the set point to the crucible lift motor controller to provide a constant melt level. An adaptive control algorithm adjusts melt temperature, via the temperature control algorithm, as required to maintain average pull rate within imposed limits. Crystal specifications are input to the computer via a card reader. Operators are required only to load the charge, read in the specification card, grow the crystal stem, initialize various procedures, and remove the crystal ingot and clean and reload the puller.

United States Patent 1 1 Cope Sept. 25, 1973 1 AUTOMATED CRYSTAL PULLING SYSTEM [75] lnventor: Edward G. Cope, Dallas, Tex.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Oct. 1, 1971 [21] Appl. No.: 185,790

[52] U.S. Cl. 235/15l.l, 23/273 SP, 148/172,

444/1 [51] Int. Cl. G06g 7/58, H011 7/40 [58] Field of Search 235/150, 151.1, 151.12;'

444/1; 23/273, 273 SP, 295, 301 SP; 29/580, 582,584, 585; 148/15, 171, 172

[56] References Cited UNITED STATES PATENTS 3.621.213 11/1971 Jen eta]. 235/150 3,493,770 2/1970 Dessauer et al. 23/273 SP 3.552.931 l/l 97l Doherty et a1. 23/273 SP 3,617,392 1 H1971 Locke 23/273 SP Primary ExaminerJoseph F. Ruggiero AltorneyHarold Levine et a1.

[57] ABSTRACT An automated crystal pulling system utilizes a digital computer to control a Czochralski crystal puller. Crystal pull rate, crystal spin rate, crucible lift rate and crucible spin rate are monitored with tachometers, and the monitored signals are applied to controllers to control the respective motors and provide independent closed control loops, with each controller having a set point signal input from the computer. A sensor detects the output level of the radio frequency generator (induction heater) and applies a signal to a generator controller having a set point input from the computer, providing closed loop temperature control. A temperature control algorithm receives an input from a melt temperature sensor and calculates the set point to the generator controller. A diameter control algorithm receives an input from a crystal diameter sensor and calculates the set point to the crystal pull motor controller. A melt level control algorithm claculates the set point to the crucible lift motor controller to provide a constant melt level. An adaptive control algorithm adjusts melt temperature, via the temperature control algorithm, as required to maintain average pull rate within imposed limits. Crystal specifications are input to the computer via a card reader. Operators are required only to load the charge, read in the specification card, grow the crystal stem, initialize various procedures, and remove the crystal ingot and clean and reload the puller.

2 Claims, 49 Drawing Figures MANUAL CONTROL PANEL PAIEN {EU SEPZS I975 SHEET 01 DF 24 4 5 L AH r m k WT M m HR TP w l 9 1 m m R mL m W m A U wmwifv fi H M/W m A ms N M c MOP 5 LHA O c c WT flol m A 2 5 N V U N H J R R i 2 u 3 H CRYSTAL PULL MECHANISM GENERATOR CRUCIBLE PATENTEU SEPZ 5 SHEET 03 0F 24 COMPUTER /3 23 I I l cHANNEL D/A cONvERTERs 25 SELECT A/D CONVERTER MULTIPLEXER k L k I 74 7/ I 3 CRUCIBLE I CONTROLLER HEIGHT OONTROLLER TRANSDUCER r75 9 J cRuOIBLE cRucIBLE SPIN LIFT 6/7 TACH TACH cYRsTAL' LENGTH TRANSDUCER 57 55 66 l I l I CRUCIBLE CRUCIELE I I CRYSTAL I SPIN LIFT PULL MOTOR MOTOR I TACH I /25 CRYSTAL PULLER J 95 65 52 r 64 I I I cRYsTAL a CONTROLLER PULL ---I-- DlAMETER I MOTOR SENSOR I I CRYSTAL I MELT cONTROLLER SPIN T TEMPERATURE I MOTOR sENsoR I27 9/ I cRw rsTAL I 33 I SPIN TACH I f l 40 l R,E, 1. I I GENERATOR J L. 63 M F/94 coNTROLLER R I=. sENsoR PATENTED E 3,761,692

saw on or 24 STALL MOTORS RF I /75 /76 W SPEC I 2 I56 AUTO 7 MAN STAT I STAT 2 STAT 3 7 no /7/ /72 V73 F/g5 /59 FROM D/A TO A D [8/ I82 SPEC LIGHT FC SPEC {83 LOAD LIGHT FROM ,84 I85 STAT I LIGHT COMPUTER FC STAT I /86 LIGHT STAT 2 LIGHT FC STAT 2 I89 LIGHT /9 7 MOTOR LIGHT Fig 8 227 MOTOR RELAY 2/5 23 7 23/ COFAPUTER I [MOTOR RF RELAY COh-PUTER RF TC ALJTG SW 8 RF LIGHT COMP PRES PATENTEU SEPZSIQH SHEU 058? 24 CRYSTAL.

GROWTH F/g,.9 250 PHASE 25/ STEM GROWTH 253 255 TOP GROWTH Z57 ROLL L CONSTANT DIAMETER GROWTH CONSTANT I G DIAMETER KGMS/SEC) 250 259 TAPER (MILS/SEC) sENsoR OUTPUT DIAMETER ERROR PAIENIED E Z 3.761.692

SHEET 06 0F 24 f LOAD LIGHT T ERMINATE CONTROL DELAY ALGORITHMS 0.5 SEC STATUS SWITCH IN AUTO SEND "RE-SEED" MESSAGE STATUS I ON SPECS LOADED TURN SPEC SEND "RUN TERMINATED" MESSAGE TURN SPEC LOAD LIGHT OF'F' PATENTEDSEPZSKJTS SHEET- 07 [1F 24 SEND "RE-START REQUIRED" MESSAGE I Hg. /4

SEND DDG-TAKEOVER" MESSAGE SEND MELT BACK INITIALIZE MESSAGE CRUCIBLE POSITION CALCULATE XKUL CALCULATE KLL.

TURN OFF Y TURN ON DELAY STAT! AND STAT OR 0.5 SEC STATZ N, HI STAT2 I N. LO

TURN ON STAT! AND STATZ PATENTEDSEP25|973 3.761.692

SHEET 08 0F 24 F/g, l6

TURN OFF SPEC LOAD LIGHT FIRST TIME THRU IRNMI =DIERR IRMIN=DIERR ENABLE MOTORS DIALL: L.L.|NI R20 DIAUL 1 ULINI I V V CLSP o PRSP vcToP PRSFA PRSFI DELAY 0.5 SECS EWITCH IN AUTO PATENTED 887255175 SHEET 09 0F 24 Fig. /6

RESET IRMIN $LOPE= IERR- IRNM1 RESET IRNM1 DIERR (IRMIN) SWITCH IN AUTO FIRST TIME THRU PRSP V ENABLE MELT LEVEL OUTPUT VCR TO PuLL MOTOR CONTROLLER IRNM1=DIERR DELAY 10 SEC PATENTED 3.761 .692

sum 10 or 24 Fig. 20 I Fig, 2/

SLOPE= DIERR-IRNMI DIAER PRSPA ENABLE DIAMETER AND PROFILE N ALGORITHMS;

CHECK LIFT MOTOR PRSP= 1. 1 (PRSP) DELAY Y 0.5 SEC PRSP PRUL DISABLE ALGORITHMS PRSP F'RSPI CLSP f O PAIENTEDSEPZ5'9T3 3.761.692

SHEET 11 0F 24 H922 Fig 23 DELAY DELAY 0.5 SEC 5.0 MIN SWITCH DECREASE IN AUTO M p GROWING TOP RFLSP KPKRF) ERRRF=RFCVF RF NLHZ ENABLE TEMP ALGORITHM MTSSP MTS PMENTEU 3,761,692

I saw 120F2 1.

FIRST TIME THRU DELAY 10 MIN NURRS MTSSP XCI XCN VCN WlTHlN LIMITS PATENIEI] SEPZS I975 CALCULAT E DIAUL AND DIALL.

DIAUL VCUL DIALL VCLL.

CALCULATE RF SET POINT sum 13 ur 24 Fig. 26

NURRS WITHlN LlMiTS NURRS MTSUL NURRS MTSLL.

MTSSP NURRS TEM1= XCN XCI TEMI BREAK POIN T= PRSPI CALCULATE VOUT PRSPA VOUT DELAY 1 MIN PATENIEDSEP25|975 3.761.692

sum 11 or 2a DELAY I0 SEC TIME TO CHECK MOTORS SET SOFTWARE FLAG CALCULATE INTEGRAL CONTROL DIAEIR WITHIN LIMITS DIAER DIALL DIAER DIAUL PMENTED SEPZSIQYS sum 15 or 24 CALCULAT E PROPORTIONAL CONTROL CALCU LAT E DERIVATIVE CONTROL CALCULATE SAVE 2 PRSPN DIALL PRSPN SAVE 2 PRSPN DIAUL DIAM ET ER CONTROL ENABLED PRSP PRSPN MOTORS ENABLED TURN ON MOTOR LIGHT START MOTORS FORWARD OUTPUT SET POINTS TO ALL MOTORS PATENTEDSEFZSISTS SHEET 18 0F 24 DELAY 1 SEC READ PULL MOTOR TACH READ CRYSTAL SPIN TACH D CRYSTAL READ CRUClBLE TRANSDUCER L EFT TACH READ CRUCIBLE SPIN TACH MOTORS AND RF TURN LIGHT cRucleLE LIFT MOTOR READ READ CRUCIBLE RF TRANsDucER SENSOR SOFTWARE FLAG Pmminsm $761,692

SM! 17 0F 24 ALREADY IN ALREADY IN ERROR SEND "MOTOR FAILURE" MESSAGE l SEND SET SOFTWARE "LOST RF FLAG POWER" SET MESSAGE SOFTWARE FLAG SET

SOFTWARE FLAG SEND "FULLER NUMBER MESSAGE PATENTEnsirzslsn Fig.36

SiiEET 18 0F 24.

Fig J7 DELAY 10 SEC DELAY O 5 SEC DELAY 0.5 SEC 1 20 Z PRSP 20 1 2.0 D ERR=- I 20 SWITCH IN AUTO SWITCH IN AUTO I Z MTSI MTS= INCREASE PRSP 5% DELAY 5 MIN PATENTEU8EP25I973 3.761.692

SHEET 19 0F 24 H9439 N Fig.40

DELAY CALCULATE 2 SEC RF sET POINT RF OUTPUT CONTROL ENABLED SET POINT TO RF CONTROLLER KNT= o TURN ON RF LIGHT ERROR RFLSP- RF ERROR WITHIN DEAD BAND KNT=KNT+1 TERMINATE RF CONTROL;

ENABLE TEMP CONTROL 

1. In a system for pulling single crystal ingots of predetermined diameter profile from a melt of material including a crystal puller of the type having heater means, means for pulling the crystal ingot from said melt as said crystal solidifies, means controlling the pull rate of said means for pulling, crystal diameter sensor means, pull rate sensor means, and melt temperature sensor means, the combination comprising: a. means responsive to change in the output of said crystal diameter sensor means to cause said means controlling the pull rate to change the pull rate of said crystal pulling means; and b. means responsive to said melt temperature sensor, said pull rate sensor, and said crystal diameter sensor to change the power input level to said heater means thereby to adjust said melt temperature and maintain the crystal pull rate within predetermined limits during the growth of said crystal ingots of predetermined diameter profile.
 2. The combination defined in claim 1 wherein said last-named means includes means determining the average pull rate of said crystal pulling means and means maintaining the average pull rate at a previously determined value. 